Photoelectric conversion apparatus and image pickup system having photoelectric conversion apparatus

ABSTRACT

A photoelectric conversion apparatus according to one aspect of the present invention includes a first substrate including a photoelectric conversion region and a surrounding region, and a second substrate including a circuit for processing a signal from the photoelectric conversion region, and overlapping the first substrate. In this case, the circuit for processing a signal from the photoelectric conversion region includes a first circuit and a second circuit with a higher drive frequency than that of the first circuit. In an orthogonal projection, the second circuit is only provided in the photoelectric conversion region.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.14/843,847, filed Sep. 2, 2015; which is a Continuation of U.S.application Ser. No. 13/742,145, filed Jan. 15, 2013, now becomes U.S.Pat. No. 9,157,796, issued Oct. 13, 2015; which claims priority fromJapanese Patent Application No. 2012-043964, filed Feb. 29, 2012, whichare hereby incorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to photoelectric conversion apparatuses inwhich a plurality of substrates are stacked.

Description of the Related Art

In recent years, CMOS type photoelectric conversion apparatuses in whicha plurality of substrates (what is called a chip) are stacked have beenstudied for size reduction and enhancement of characteristics. JapanesePatent Laid-Open No. 2011-159958 discloses a stacked photoelectricconversion apparatus including a first chip having pixels and a circuitrequired to have an analog characteristic and/or a noise characteristicand a second chip having a circuit that runs fast with a low voltage.

SUMMARY OF THE INVENTION

A photoelectric conversion apparatus according to one aspect of thepresent invention includes a first substrate including a photoelectricconversion region including a photoelectric conversion element and acircuit for reading a signal from the photoelectric conversion region,and a surrounding region, and a second substrate including a circuit forprocessing a signal from the photoelectric conversion region, andoverlapping the first substrate. In this case, the circuit forprocessing a signal from the photoelectric conversion region includes afirst circuit and a second circuit with a higher drive frequency thanthat of the first circuit. In an orthogonal projection, the secondcircuit is only provided in the surrounding region.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram for describing an overall photoelectricconversion apparatus of a first embodiment, FIG. 1B is a block diagramfor describing a first substrate of the photoelectric conversionapparatus of the first embodiment, FIG. 1C is a block diagram fordescribing a second substrate of the photoelectric conversion apparatusof the first embodiment, and FIG. 1D is a schematic cross-sectiondiagram for describing the overall photoelectric conversion apparatus ofthe first embodiment.

FIG. 2A is a block diagram for describing an overall photoelectricconversion apparatus of a second embodiment, FIG. 2B is a block diagramfor describing a first substrate of the photoelectric conversionapparatus of the second embodiment, and FIG. 2C is a block diagram fordescribing a second substrate of the photoelectric conversion apparatusof the second embodiment.

FIG. 3A is a block diagram for describing an overall photoelectricconversion apparatus of a third embodiment, FIG. 3B is a block diagramfor describing a first substrate of the photoelectric conversionapparatus of the third embodiment, and FIG. 3C is a block diagram fordescribing a second substrate of the photoelectric conversion apparatusof the third embodiment.

FIG. 4A is a block diagram for describing an overall photoelectricconversion apparatus of a fourth embodiment, FIG. 4B is a block diagramfor describing a first substrate of the photoelectric conversionapparatus of the fourth embodiment, and FIG. 4C is a block diagram fordescribing a second substrate of the photoelectric conversion apparatusof the fourth embodiment.

FIG. 5A is a block diagram for describing an overall photoelectricconversion apparatus of a fifth embodiment, FIG. 5B is a block diagramfor describing a first substrate of the photoelectric conversionapparatus of the fifth embodiment, and FIG. 5C is a block diagram fordescribing a second substrate of the photoelectric conversion apparatusof the fifth embodiment.

FIG. 6A is a block diagram for describing an overall photoelectricconversion apparatus of a sixth embodiment, FIG. 6B is a block diagramfor describing a first substrate of the photoelectric conversionapparatus of the sixth embodiment, FIG. 6C is a block diagram fordescribing a second substrate of the photoelectric conversion apparatusof the sixth embodiment, FIG. 6D is a block diagram for describing athird substrate of the photoelectric conversion apparatus of the sixthembodiment, and FIG. 6E is a schematic cross-section diagram fordescribing the overall photoelectric conversion apparatus of the sixthembodiment.

FIG. 7A is a block diagram for describing an overall photoelectricconversion apparatus of a seventh embodiment, FIG. 7B is a block diagramfor describing a first substrate of the photoelectric conversionapparatus of the seventh embodiment, FIG. 7C is a block diagram fordescribing a second substrate of the photoelectric conversion apparatusof the seventh embodiment, and FIG. 7D is a block diagram for describinga third substrate of the photoelectric conversion apparatus of theseventh embodiment.

DESCRIPTION OF THE EMBODIMENTS

The present inventors have found in the configuration of Japanese PatentLaid-Open No. 2011-159958 that heat generated in circuits may increasenoise and reduce image quality. This is because of an increase of darkframe noise in a photoelectric conversion region where heats of circuitsmay overlap. Accordingly, a photoelectric conversion apparatus accordingto an embodiment of the present invention may provide a stackedphotoelectric conversion apparatus with reduced noise.

A photoelectric conversion apparatus according to a plurality ofembodiments includes a first substrate and a second substrate. The firstsubstrate includes a photoelectric conversion region and a surroundingregion. The second substrate includes a circuit that processes a signalfrom the photoelectric conversion region and overlaps the firstsubstrate. The circuit that processes a signal from the photoelectricconversion region includes a first circuit and a second circuit with ahigher drive frequency than the first circuit. In the orthogonalprojection, the second circuit is provided in the surrounding region.

Providing circuits that generate heat externally to the photoelectricconversion region in the configuration may inhibit an increase of noise.

An unbalanced arrangement of circuits that generate heat in a plane ofthe photoelectric conversion region may possibly cause large imageirregularities. This is because a heat distribution occurs in a plane ofthe photoelectric conversion region, which then causes a distribution ofdark frame noise. On the other hand, a uniform arrangement of circuitsin the photoelectric conversion region may reduce noise irregularities.

The photoelectric conversion region has a plurality of pixels includinga photoelectric conversion element and includes a photoelectricconversion element and a circuit for reading a signal from thephotoelectric conversion element. The photoelectric conversion regionmay also be called an image region. A signal from the photoelectricconversion region may be used for imaging, focal point detection orilluminance detection. For example, in a CMOS photoelectric conversionapparatus, the photoelectric conversion region has an array of pixelscontaining photodiodes that are photoelectric conversion elements and/oran array of pixel cells containing a plurality of photoelectricconversion elements. For example, a current source provided for eachcolumn or a pixel drive circuit provided for each row is not included inthe photoelectric conversion region.

The surrounding region is a part of the first substrate having thephotoelectric conversion region and excludes the photoelectricconversion region. The surrounding region may have a circuit thatprocesses a signal from the photoelectric conversion region, like thesecond substrate.

Each of the first substrate and the second substrate contain asemiconductor substrate, a wiring layer, and an insulating layer. Thesurface closer to the wiring layer of the substrate will be called afront side, and the opposite surface will be called a back side. Thesurface having an element of a semiconductor substrate such as aboundary face against a gate insulating layer of a MOS transistor willbe called a principal face. In the following embodiments, the orthogonalprojection is assumed to be projected toward the principal face of thesecond substrate. The expression, “circuit overlaps a certain region” or“circuit is provided in a certain region”, means that a circuit isprovided in a region in the orthogonal projection projected toward theprincipal face of the second substrate. Alternatively, it means that theorthogonal projections of a circuit and a region to the principal faceof the second substrate overlap. A plane of a semiconductor substrate onwhich an element is provided, that is, an element-formed-range of theprincipal face is regarded as a range where a circuit is provided. Inthe following embodiments, the first substrate and the second substrateare assumed to overlap such that a front side of the first substrate anda front side of the second substrate may face against each other.However, any sides may face against each other when the first substrateand the second substrate overlap.

Embodiments will be described below more specifically with reference todrawings.

First Embodiment

A photoelectric conversion apparatus according to a first embodimentwill be described with reference to FIGS. 1A to 1D. First of all, withreference to FIG. 1A, an overall photoelectric conversion apparatus ofthis embodiment will be described.

FIG. 1A is a block diagram for describing the overall photoelectricconversion apparatus. The photoelectric conversion apparatus has aphotoelectric conversion region 103. The photoelectric conversion region103 has a plurality of pixels containing a photoelectric conversionelement and performs photoelectric conversion for imaging. Thephotoelectric conversion region 103 has a column signal line foroutputting a signal from a pixel. In other words, the photoelectricconversion region includes pixels and a column signal line. Each of thepixels includes at least one photoelectric conversion element and acircuit for reading a signal from the photoelectric conversion element.Each of the pixels according to this embodiment contains a transfertransistor, a reset transistor, and a source follower transistorincluded in a source follower circuit but may be configured arbitrarily.In other words, each of the pixels includes a transfer transistor, areset transistor and a source follower transistor included in a sourcefollower circuit, as a circuit for reading a signal from thephotoelectric conversion element.

The photoelectric conversion apparatus further includes a column circuit104, a comparing circuit 105, a reference power supply circuit 106, acounter circuit 107, a timing generator circuit (hereinafter called a TGcircuit) 108, a signal holding circuit 109, a horizontal scanningcircuit 110, a vertical scanning circuit 111, and a pixel drive circuit112. The column circuit 104 is provided for each column signal line andincludes a current source included in a source follower circuit. Thecolumn circuit 104 may have an amplifying unit that is provided for eachcolumn. The comparing circuit 105, reference power supply circuit 106,counter circuit 107, and signal holding circuit 109 may convert a signalthat is an analog signal from the photoelectric conversion region 103 toa digital signal. In other words, they may function as an analog-digitalconverter. Notably, the comparing circuit 105 may also be called acomparator. The reference power supply circuit may supply referencevoltage having a RAMP waveform, but the reference power supply circuitmay have a digital-analog converter (DAC). The TG circuit 108 maygenerate a control signal that controls operations of the verticalscanning circuit 111, column circuit 104, reference power supply circuit106, and horizontal scanning circuit 110. The pixel drive circuit 112generates a signal for driving a transistor in a pixel on the basis of asignal from the vertical scanning circuit 111. The horizontal scanningcircuit 110 controls an operation of sequentially reading signals basedon a plurality of signal lines (column signal lines here) processed inparallel to a common signal line. According to this embodiment, thesignal holding circuit 109 includes the common signal line. The signalholding circuit 109 further includes a plurality of signal holdingelements such as what is called a memory. The signal holding circuit 109may further include an adder element. A circuit that processes a signalfrom the photoelectric conversion region is a circuit that amplifies andconverts a signal and may be the column circuit 104, comparing circuit105, signal holding circuit 109, analog-digital converter or the like.

The photoelectric conversion apparatus according to this embodiment hasan image signal processing unit 113. The image signal processing unit113 has an image signal processing circuit 114, a microprocessor 115 anda signal holding circuit 116. The signal holding circuit 116 includes aplurality of memories, what is called signal holding elements, like thesignal holding circuit 109. The photoelectric conversion apparatus hasan input interface (hereinafter called an input IF) 117 and an outputinterface (hereinafter, called an output IF) 118.

In the photoelectric conversion apparatus of this embodiment, thecomponents are provided on two substrates.

FIG. 1D schematically illustrates a cross-section of the two substratesin the photoelectric conversion apparatus of this embodiment. A firstsubstrate 101 has a front side 120 and a back side 190, and a secondsubstrate 102 has a front side 121 and a back side 122. The twosubstrates are connected or adhered such that the front side 120 of thefirst substrate 101 and the front side 121 of the second substrate 102may face against each other to acquire the construction in FIG. 1D.These two substrates may be electrically coupled with athrough-electrode or a bump. A photoelectric conversion apparatus ofthis embodiment is what is called a backside illuminated photoelectricconversion apparatus in which light 123 enters to the back side 119 ofthe first substrate 101.

FIG. 1B and FIG. 1C are block diagrams for describing the firstsubstrate and the second substrate. FIG. 1B and FIG. 1C are schematicdiagrams when the configurations of the substrates are projected to theprincipal face of the second substrate and may be called plane layoutsof the substrates. It is assumed here that the projection is performedfrom the direction indicated by the light “123” in FIG. 1D.

The first substrate 101 has, as illustrated in FIG. 1B, thephotoelectric conversion region 103 and current sources 104 a that areparts of the column circuit 104. The current source 104 a is provided inthe surrounding region 129 excluding the photoelectric conversion region103. The surrounding region 129 has a first part 129 a and a second part129 b across the photoelectric conversion region 103. Two currentsources 104 a are provided across the photoelectric conversion region103. In other words, the current sources 104 a are provided on two sidesin the X axis direction of the rectangular photoelectric conversionregion 103 that has sides in the X axis direction and sides in Y axisdirection. In this case, the two current sources 104 a are preferablyequivalent circuit to increase the symmetry.

The second substrate 102 has components other than the photoelectricconversion region 103 and the current sources 104 a, as illustrated inFIG. 1C. More specifically, the second substrate 102 has an amplifyingunit 104 b that is a part of the column circuit 104, the comparingcircuit 105, the reference power supply circuit 106, the counter circuit107, the TG circuit 108, the signal holding circuit 109, a horizontalscanning circuit 110, the vertical scanning circuit 111, and the pixeldrive circuit 112. The second substrate 102 further includes the inputIF 117 and the output IF 118. An overlapping area 130 that overlaps thephotoelectric conversion region 103 in the orthogonal projection whenthe first substrate 101 and the second substrate 102 overlap, includes afirst circuit that is driven by a first clock. The first circuitincludes the amplifying unit 104 b, comparing circuit 105, TG circuit108, vertical scanning circuit 111, and pixel drive circuit 112. Thesecircuits overlap the photoelectric conversion region 103. In otherwords, the first circuit is provided in the photoelectric conversionregion 103 in an orthogonal projection projected to the principal faceof the second substrate 102. The other area 131 b includes a secondcircuit that is driven by a second clock having a higher frequency thanthat of the first clock. That is, the second circuit is driven by ahigher drive frequency than the first circuit. The second circuitincludes the reference power supply circuit 106, counter circuit 107,signal holding circuit 109, horizontal scanning circuit 110, imagesignal processing unit 113, input IF 117, and output IF 118. Thesecircuits are not provided in the photoelectric conversion region 103 inthe orthogonal projection projected toward the principal face of thesecond substrate 102 but are only provided in the surrounding region129. According to this embodiment, the second circuit includes thecounter circuit 107 and horizontal scanning circuit 110. Thisconfiguration may provide a stacked photoelectric conversion apparatusthat reduces noise.

The second circuit exhibits a high heating value because it has a higherdrive frequency and higher power consumption than the first circuit.Thus, the overlap of the circuit that functions as a heat source and thephotoelectric conversion region 103 may transfer heat to thephotoelectric conversion region 103 and increase noise. For example,even when a part of the circuit is provided in the photoelectricconversion region 103 in the orthogonal projection, heat is transferredto parts of the photoelectric conversion region 103, which may possiblycause image irregularities. Therefore, at least the second circuit onthe second substrate 102 is desirably provided only in the surroundingregion 129 in the orthogonal projection.

Here, for example, the first clock relates to a vertical scanning speed,and the second clock relates to horizontal scanning. For example, thefirst clock may be a clock for driving a part that processes signals oroperations in parallel. The second clock may be a clock for driving apart that performs processing on signals or operations upon shift fromparallel processing to serial processing. Thus, the first clock has ahigher frequency than that of the second clock. More specifically, thesecond clock has a higher frequency of the first clock by a factor of100 or higher, such as 500 or even 1200.

The area of the counter circuit 107 is generally a hundredth of the areaof the photoelectric conversion region 103, and it is difficult touniformly arrange the counter circuit 107 on the photoelectricconversion region 103. Providing the counter circuit 107 for each columnmay sometimes cause a heat distribution because signals may consumedifferent amounts of current. The horizontal scanning circuit 110 may bea shift register circuit or a decoder, for example, which may have aquarter area of the area of the photoelectric conversion region 103.Therefore, it is difficult to uniformly arrange the horizontal scanningcircuit 110 on the photoelectric conversion region 103. Ununiformarrangement thereof may cause irregularities and/or streaky noise, whichmay possibly deteriorate the image quality. The second circuit whoseorthogonal projected area having a half area of the area of theorthogonal projected area of the photoelectric conversion region isdesirably arranged to superpose upon the surrounding region 129 of thefirst substrate 101.

According to this embodiment, the surrounding region 129 includes thefirst part 129 a and the second part 129 b, and the overlapping area 131includes a third part 131 a that correspondingly overlaps the first part129 a and a fourth part 131 b that correspondingly overlaps the secondpart 129 b. Any circuits provided in the first part 129 a and secondpart 129 b are the current sources 104 a and are equivalent circuits.Circuits provided in the third part 131 a and fourth part 131 b are alsothe reference power supply circuit 106, counter circuit 107, signalholding circuit 109, horizontal scanning circuit 110, image signalprocessing unit 113, and output IF 118 and are equivalent circuits.These configurations may increase the symmetry of the signal outputpaths and may increase the image quality.

According to this embodiment, the reference power supply circuits 106are further provided in the overlapping area 131. Each of the referencepower supply circuits 106 may possibly be a heat source when it is a DACor has many resistances, for example. Because the reference power supplycircuits 106 generally have a tenth area of the photoelectric conversionregion 103, it is difficult to arrange the reference power supplycircuits 106 uniformly in the photoelectric conversion region 103.Providing such circuits in the overlapping area 131 may allow furtherreduction of noise of the photoelectric conversion apparatus.

The overlapping area 130 further has two comparing circuits 105 acrossthe amplifying unit 104 b and has the TG circuit 108 and the verticalscanning circuit 111 across the amplifying unit 104 b. Providing the twocomparing circuits 105 may increase the symmetry and allow output ofsignals from the two output IFs 118, which may increase the readingspeed.

Because the image signal processing unit 113 includes the microprocessor115 and the image signal processing circuit 114 that are driven by ahigher frequency than that of the first clock, it is desirably providedin the other area 131. However, the image signal processing unit 113having a larger area may be provided in the photoelectric conversionregion in an orthogonal projection toward the second substrate in theprincipal face by disposing circuits such that the heating parts may bearranged uniformly within the image signal processing unit 113. Theimage signal processing unit 113 may be provided externally to thephotoelectric conversion apparatus.

The surrounding region 129 may only be required to exclude thephotoelectric conversion region 103 and is not limited to the regionaccording to this embodiment.

Second Embodiment

A photoelectric conversion apparatus of a second embodiment will bedescribed with reference to FIGS. 2A, 2B and 2C. FIGS. 2A, 2B and 2Ccorrespond to FIGS. 1A, 1B and 1C. FIG. 2A corresponds to FIG. 1A, FIG.2B corresponds to FIG. 1B, and FIG. 2C corresponds to FIG. 1C. Likenumbers refer to like components, and the descriptions will be omitted.The photoelectric conversion apparatus of this embodiment is differentfrom the photoelectric conversion apparatus of the first embodiment inthe arrangement of circuits in an overlapping area 230 overlapping thephotoelectric conversion region 103 and circuits provided in thesurrounding region 229 of the first substrate 101.

The photoelectric conversion apparatus of this embodiment includes, asillustrated in FIG. 2A and FIG. 2B, a photoelectric conversion region103 and a column circuit 104 having both of the current source 104 a andthe amplifying unit 104 b of the first embodiment on the first substrate101. In other words, the surrounding region 229 of this embodimentincludes the column circuit 104. As illustrated in FIG. 2C, anoverlapping area 230 overlapping the photoelectric conversion region 103of the second substrate 102 includes the comparing circuit 105, the TGcircuit 108, the vertical scanning circuit 111, the pixel drive circuit112, and a non-circuit part 224. The non-circuit part 224 is a partwhere no circuit is provided. Arranging the non-circuit part 224 overthe photoelectric conversion region 103 may allow reduction of noise ofthe photoelectric conversion region 103.

Also according to this embodiment, the vertical scanning circuit 111 andthe pixel drive circuit 112 are provided with respect to a side in the Yaxis direction of the photoelectric conversion region 103 and receive asignal for driving pixels from a side in the Y axis direction of thephotoelectric conversion region 103. This configuration may allow supplyof a signal for driving pixels to the photoelectric conversion region103 in the shortest distance.

Two comparing circuits 105 and signal holding circuits 109 are providedin the Y axis direction (vertical direction) in the overlapping areas230 and 231 so that signals from the photoelectric conversion region 103may be distributed in the Y axis direction (vertical direction) to beprocessed. In other words, the reading speed may be increased, like thefirst embodiment.

Third Embodiment

A photoelectric conversion apparatus according to a third embodimentwill be described with reference to FIGS. 3A to 3C. FIGS. 3A to 3Ccorrespond to FIGS. 1A to 1C and FIGS. 2A to 2C. The third embodimentwill be described by comparing FIGS. 3A to 3C with FIGS. 2A to 2C(second embodiment). FIG. 3A corresponds to FIG. 2A, FIG. 3B correspondsto FIG. 2B, and FIG. 3C corresponds to FIG. 2C. Like numbers refer tolike components, and the descriptions will be omitted. The photoelectricconversion apparatus of this embodiment is different from thephotoelectric conversion apparatus of the second embodiment in thearrangement of circuits in an overlapping area 330 overlapping thephotoelectric conversion region 103. Because FIG. 3A and FIG. 3B are thesame as FIG. 2A and FIG. 2B, the descriptions will be omitted.

The photoelectric conversion apparatus of this embodiment includes, asillustrated in FIG. 3C, the TG circuit 108, the vertical scanningcircuit 111, the pixel drive circuit 112, and the non-circuit part 224,excluding the comparing circuit 105, in the overlapping area 330overlapping the photoelectric conversion region 103 of the secondsubstrate 102. In other words, the first circuit does not have thecomparing circuit 105 but includes the TG circuit 108, vertical scanningcircuit 111, pixel drive circuit 112, and non-circuit part 224. Thisconfiguration also according to this embodiment may allow reduction ofnoise of the photoelectric conversion apparatus.

In the Y axis direction, two overlapping areas 331 are provided acrossthe overlapping area 330. Circuits are arranged in the overlapping areas331 with high symmetry, and signals from the photoelectric conversionregion 103 are distributed in the Y axis direction (vertical direction)to be processed.

The signal holding circuit may sometimes have an equal area to the areaof the photoelectric conversion region 103. In that case, thenon-circuit part 224 is preferably provided.

Fourth Embodiment

A photoelectric conversion apparatus according to a fourth embodimentwill be described with reference to FIGS. 4A to 4C. FIGS. 4A to 4Ccorrespond to FIGS. 1A to 1C to FIGS. 3A to 3C. The fourth embodimentwill be described by comparing FIGS. 4A to 4C with FIGS. 1A to 2C(second embodiment). FIG. 4A corresponds to FIG. 2A, FIG. 4B correspondsto FIG. 2B, and FIG. 4C corresponds to FIG. 2C. Like numbers refer tolike components, and the descriptions will be omitted. The photoelectricconversion apparatus of this embodiment is different from thephotoelectric conversion apparatus of the second embodiment inarrangement of circuits in the overlapping area 430 overlapping thephotoelectric conversion region 103 and circuits provided in thesurrounding region 429 of the first substrate 101.

The photoelectric conversion apparatus of this embodiment includes thephotoelectric conversion region 103, the column circuit 104, thevertical scanning circuit 111, and the pixel drive circuit 112 on thefirst substrate 101 as illustrated in FIG. 4A and FIG. 4B. In otherwords, the surrounding region 229 of this embodiment includes the columncircuit 104, vertical scanning circuit 111, and pixel drive circuit 112.As illustrated in FIG. 4C, the comparing circuit 105 and TG circuit 108are only arranged in the overlapping area 430 overlapping thephotoelectric conversion region 103 of the second substrate 102. Inother words, the first circuit includes the comparing circuit 105 andthe TG circuit 108. This configuration allows reduction of noise of thephotoelectric conversion apparatus also according to this embodiment.

Furthermore, according to this embodiment, one output IF 118 isprovided, and the number of terminals may be reduced.

Fifth Embodiment

A photoelectric conversion apparatus of this embodiment will bedescribed with reference to FIGS. 5A to 5C. FIGS. 5A to 5C correspond toFIGS. 1A to 1D to FIGS. 4A to 4C. The fifth embodiment will be describedby comparing FIGS. 5A to 5C with FIGS. 4A to 4C (fourth embodiment).FIG. 5A corresponds to FIG. 4A, FIG. 5B corresponds to FIG. 4B, and FIG.5C corresponds to FIG. 4C. Like numbers refer to like components, andthe descriptions will be omitted. The photoelectric conversion apparatusof this embodiment is different from the photoelectric conversionapparatus of the fourth embodiment in arrangement of circuits in theoverlapping area 430 overlapping the photoelectric conversion region 103and circuits provided in the surrounding region 529 of the firstsubstrate 101.

The photoelectric conversion apparatus of this embodiment includes thephotoelectric conversion region 103, the column circuit 104, thevertical scanning circuit 111, and the pixel drive circuit 112 on thefirst substrate 101 as illustrated in FIG. 5A and FIG. 5B. Thesurrounding region 229 of this embodiment includes the vertical scanningcircuit 111, and pixel drive circuit 112. In other words, thisembodiment is different from the fourth embodiment in that the columncircuit 104 is not provided on the first substrate 101. As illustratedin FIG. 5C, the column circuit 104, comparing circuit 105 and TG circuit108 are arranged in an overlapping area 530 overlapping thephotoelectric conversion region 103 of the second substrate 102. Inother words, the first circuit includes the column circuit 104,comparing circuit 105 and the TG circuit 108. This configuration allowsreduction of noise of the photoelectric conversion apparatus alsoaccording to this embodiment.

Sixth Embodiment

A photoelectric conversion apparatus according to a sixth embodimentwill be described with reference to FIGS. 6A to 6E. This embodiment willbe described by comparing FIGS. 6A to 6E with FIGS. 1A to 1D (firstembodiment). FIG. 6A corresponds to FIG. 1A, FIG. 6B corresponds to FIG.1B, FIG. 6C corresponds to FIG. 1C, and FIG. 6E corresponds to FIG. 1E.FIG. 6D is a block diagram illustrating a third substrate which is newlyprovided in this embodiment. Like numbers refer to like components, andthe descriptions will be omitted. The photoelectric conversion apparatusof this embodiment is largely different from the photoelectricconversion apparatus of the first embodiment in that the sixthembodiment has a third substrate 603.

As illustrated in FIG. 6A, the image signal processing unit 113 and theoutput IF 118 are provided on the third substrate 603 of thisembodiment. The third substrate 603 is arranged to overlap the firstsubstrate 101 and the second substrate 102. As illustrated in FIG. 6E, aface 626 of the third substrate 603 having a front side 626 and a backside 627 is provided in contact with the back side 122 of the secondsubstrate 102.

In the photoelectric conversion apparatus, the first substrate 101 onlyhas the photoelectric conversion region 103, and a surrounding region629 does not have a circuit and so on. The second substrate 102 includesthe column circuit 104, comparing circuit 105, TG circuit 108, verticalscanning circuit 111, pixel drive circuit 112, reference power supplycircuit 106, counter circuit 107, signal holding circuit 109, horizontalscanning circuit 110, and input IF 117. An overlapping area 630overlapping the photoelectric conversion region 103 has the columncircuit 104, comparing circuit 105, TG circuit 108, vertical scanningcircuit 111, and pixel drive circuit 112, which are included in a firstcircuit. The other overlapping area 631 including a second circuitoverlaps the surrounding region 629. The third substrate 603 has theimage signal processing unit 113 and the output IF 118. The image signalprocessing unit 113 may often include a microprocessor 115 and/or imagesignal processing circuit 114 which may process a signal in synchronismwith a clock having a higher frequency than that of the second clock.However, because the second substrate 102 is provided between the thirdsubstrate 603 and the first substrate 101 having the photoelectricconversion region 103, the image signal processing unit 113 is lessinfluenced by heat. Therefore, the photoelectric conversion region 103and the image signal processing unit 113 may be arranged to superposeone upon the other. This configuration allows reduction of noise of thephotoelectric conversion apparatus also according to this embodiment.

Seventh Embodiment

A photoelectric conversion apparatus according to a fourth embodimentwill be described with reference to FIGS. 7A to 7D. The seventhembodiment will be described by comparing FIGS. 7A to 7D with FIGS. 6Ato 6D (sixth embodiment). FIG. 7A corresponds to FIG. 6A, FIG. 7Bcorresponds to FIG. 6B, FIG. 7C corresponds to FIG. 6C, and FIG. 7Dcorresponds to FIG. 6D. Like numbers refer to like components, and thedescriptions will be omitted. The photoelectric conversion apparatus ofthis embodiment is different from the photoelectric conversion apparatusof the sixth embodiment in circuits provided on the first substrate 101and circuits provided in an overlapping area 730 overlapping thephotoelectric conversion region 103. Because the same as the sixthembodiment is true for the third substrate 603 of the photoelectricconversion apparatus of this embodiment, the description will beomitted.

As illustrated in FIG. 7A and FIG. 7B, the first substrate 101 of thisembodiment has the photoelectric conversion region 103 and columncircuit 104. In other words, the column circuit 104 is provided in asurrounding region 729. An overlapping area 730 of the second substrate102 is a non-circuit part 724 where no circuits are arranged. Thisconfiguration also allows reduction of noise of the photoelectricconversion apparatus.

An image pickup system including the photoelectric conversion apparatusas described above will be described as application examples of thephotoelectric conversion apparatus. The concept of the image pickupsystem includes not only an apparatus (such as a still camera and acamcoder) whose main purpose is imaging but also an apparatus (such as apersonal computer and a mobile terminal) having an imaging functionauxiliarily. The image pickup system includes a photoelectric conversionapparatus described according to one of the aforementioned embodimentsand a processing unit that processes a signal output from thephotoelectric conversion apparatus. Alternatively, the image pickupsystem may have an optical system (such as a lens) for forming an imagein a photoelectric conversion apparatus described according to one ofthe aforementioned embodiments.

As described according to the aforementioned embodiments, aphotoelectric conversion apparatus according to any one of theaforementioned embodiments may allow reduction of noise and may providehigh quality images.

A photoelectric conversion apparatus of the present invention is notlimited to the aforementioned embodiments. For example, the embodimentsmay be changed and/or combined properly.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

What is claimed is:
 1. A photoelectric conversion apparatus, comprising:a first substrate that includes a photoelectric conversion region onwhich a plurality of pixels is provided in a two-dimensional array, eachof the plurality of pixels including a photoelectric conversion element;a second substrate that includes a vertical scanning circuit; and athird substrate that includes an image signal processing unit, whereinthe first substrate, the second substrate, and the third substrate arestacked.
 2. The photoelectric conversion apparatus according to claim 1,wherein the photoelectric conversion region and the image signalprocessing unit overlap with each other in plan view.
 3. Thephotoelectric conversion apparatus according to claim 1, wherein thephotoelectric conversion region and the vertical scanning circuitoverlap with each other in plan view.
 4. The photoelectric conversionapparatus according to claim 1, wherein the photoelectric conversionregion and a comparing circuit of an analog-digital converter overlapwith each other in plan view.
 5. The photoelectric conversion apparatusaccording to claim 4, wherein the comparing circuit is provided on thesecond substrate.
 6. The photoelectric conversion apparatus according toclaim 1, wherein the third substrate has an output interface.
 7. Thephotoelectric conversion apparatus according to claim 1, wherein thesecond substrate has an input interface.
 8. The photoelectric conversionapparatus according to claim 1, further comprising: a timing generatorcircuit; wherein the photoelectric conversion region and the timinggenerator circuit overlap with each other in plan view.
 9. Thephotoelectric conversion apparatus according to claim 1, furthercomprising: a non-circuit part; wherein the photoelectric conversionregion and the non-circuit part overlap with each other in plan view.10. An image pickup system, comprising: the photoelectric conversionapparatus according to claim 1; and a processing circuit for processinga signal from the photoelectric conversion apparatus.
 11. Aphotoelectric conversion apparatus, comprising: a first substrate thatincludes a photoelectric conversion region on which a plurality ofpixels is provided in a two-dimensional array, each of the plurality ofpixels including a photoelectric conversion element; a second substratethat includes a pixel drive circuit for generating a signal for drivingthe pixel; and a third substrate that includes an image signalprocessing unit, wherein the first substrate, the second substrate, andthe third substrate are stacked.
 12. The photoelectric conversionapparatus according to claim 11, wherein the photoelectric conversionregion and the image signal processing unit overlap with each other inplan view.
 13. The photoelectric conversion apparatus according to claim11, wherein the photoelectric conversion region and the pixel drivecircuit overlap with each other in plan view.
 14. The photoelectricconversion apparatus according to claim 11, wherein the photoelectricconversion region and a comparing circuit of an analog-digital converteroverlap with each other in plan view.
 15. The photoelectric conversionapparatus according to claim 14, wherein the comparing circuit isprovided on the second substrate.
 16. The photoelectric conversionapparatus according to claim 11, wherein the third substrate has anoutput interface.
 17. The photoelectric conversion apparatus accordingto claim 11, wherein the second substrate has an input interface. 18.The photoelectric conversion apparatus according to claim 11, furthercomprising: a timing generator circuit; wherein the photoelectricconversion region and the timing generator circuit overlap with eachother in plan view.
 19. The photoelectric conversion apparatus accordingto claim 11, further comprising: a non-circuit part; wherein thephotoelectric conversion region and the non-circuit part overlap witheach other in plan view.
 20. An image pickup system, comprising: thephotoelectric conversion apparatus according to claim 11; and aprocessing circuit for processing a signal from the photoelectricconversion apparatus.